Electric arc furnace



Dec. 3,v 1946. W E 'MOORE 2,412,000

ELECTRIC ARC FURNAGE Filed Jan. 5l, 1945 i l l INVENTOR Patented Dec. 3,1946 UNITED STATES PATENT OFFICE ELECTRIC ARC FURNACE William E. Moore,Pittsburgh, Pa., assigner to Delaware Engineering Corporation,Pittsburgh, Pa., a corporation of Delaware Application January 31, 1945,Serial No. 575,406

(Cl. S14-61) 7 Claims. 1

This invention pertains to electric arc furnaces and is for an electrodeoperating apparatus and method for such furnaces. The applicationconstitutes a continuation-in-part of my application Serial No. 498,317,nled August l2, 1943.

As disclosed in my said application it has been proposed to mount thecarbon electrode of a furnace on any suitable form of guideway operatedby a piston movable in a cylinder or by any desired form of fluid motor.The cylinder is connected through a reversing pump with a reservoir withmeans for confining air under pressure in the reservoir. The reversingpump is driven by a reversing electric motor, which in turn iscontrolled by the current being supplied to the electrode by well knownmeans, so that if the arc lengthens the pump is driven to remove liquidfrom the cylinder and return it to the reservoir, whereas ii the arcshortens, the pump is driven in a direction to force liquid from thereservoir into the cylinder to lift the electrode and increase thelength of the arc. The air over the reservoir is kept at a pressureslightly less than that necessary to counterbalance the electrodeassembly, including the piston, so that the pump merely works against aslight differential in pressure.

According to the present invention, the pressure in the reservoir ismaintained somewhat higher, instead of lower, than that necessary tocounterbalance the electrode assembly. This has in some cases certainimportant values. If there is a current interruption or failure, theelectrode is lifted clear of the charge in the furnace, avoidingcarbonization of the charge which results when the electrode drops andremains in the charge. If the control mechanism fails, the electrodelikewise is raised.

My invention further provides an improved arrangement for cooling theoil or other liquid used in the system.

The invention may be more fully understood by reference to theaccompanying drawing in which the gure is a more or less schematic Viewof an electric furnace embodying my invention.

In the drawing, the furnace 2 is of conventional form. A singleelectrode is indicated at 3, but, there may be any desired number ofsuch electrodes, three commonly being used, but for present purposes oneis suicient. The electrode 3 is carried on a supporting arm 4 at the topof a piston 5 operating in a cylinder 6, the piston serving as a meansfor raising or lowering the electrode. Power from a line 1 is suppliedthrough cable 8.

Connected with the bottom of the cylinder is a pipe 9 leading to oneside of a reversible metering pump i8 which is of any usual or preferredconstruction. It may ce of the familiar gear or eccentric vane type, andin either case is incapable of completely blocking the flow or" iiuidtherethrough, and may be capable of being operated by the fluid pressurein the line.

The opposite side of the pump l@ is connected with a pipe I i, and at l2 is a huid pressure reservoir. Pipe Il has one branch Ha leadingthrough check valve i3 to a spray nozzle or distributor lli inside thetop of the reservoir. Another branch, l5, leads from pipe ll through acheck valve iii to the bottom of the reservoir, Check valve Iii permitsoutflow from the reservoir but not inn flow, and check valve i3 permitsiniiow, but not out-now.

A compressor Il maintains a pressure on the liquid I8 in the reservoir,which pressure is maintained at a substantially uniform value, thispressure being suiiicient, when transmitted through the pump, eventhough the pump is not being driven, to overloalance the electrodemounting` assembly and raise the electrode.

The reversible pump lil is driven by a re versble motor which iscontrolled by a control unit 2| electromagnetically or electronically operated by the current and/or voltage supplied the electrode, asindicated, controls of this kind being well known in the art and beingcormnercially available through Westinghouse Electric and ManufacturingCompany, General Electric Company, Allis-Chalmers, and others.

In operation the motor 20 drives the pump one way or the other to eiiectthe raising and lowering of the electrode according to variations in thecurrent. Since the pressure in the reservoir is only slightly higherthan the pressure created by the piston on the liquid in the cylinder,the pump has only to work at the most against a relatively slightdifferential to overcome resistance and raise or lower the electrode andthe system responds readily to any need for adjustment.

As previously stated, metering pumps such as l0 are not fluid tight, orthey may be rotated by a diierential pressure in the fluid system. Thisis a definite advantage, because when the pump is not operating thesuperior pressure in the reservoir is effective, but slowly however,against the piston to urge it very gradually upward. Hence, if currentto the electrode is interrupted or the control unit fails to operate,the electrode will be gradually lifted to a point well clear of thecharge in the furnace. At the same time, the effect of 56 this superiorcounter pressure is such, by reason of the pump, that movement of theelectrode upwardly is very gradual when the pump is not working. Whenthe pump is working, the movement of the electrode in either directionmay take place more or less rapidly.

When the pump is operating to lower the electrode, the oil or otherliquid withdrawn from the cylinder cannot enter the reservoir throughcheck valve I8 and hence, must be discharged through spray nozzle it,which sprays it against the sides of the reservoir to cool it. Theliquid becomes hot, not only by reason of the more or less frequentoperation of the pump, but by reason oiV the cylinder being in proximityto the furnace, and this cooling of the liquid is a desirable feature ofmy invention. On the other hand, I3 prevents back flow of air into thesystem.

While I have shown as a preferred embodiment of my invention, a systemin which a superior pressure is maintained in the reservoir by reason ofair pressure maintained on a confined space above the liquid, otherfamiliar means of securing the same result, as 'cy elevating thereservoir to secure a desired hydrostatic pressure head may be employed,and the invention may be otherwise embodied within the scope of thefollowing claims.

I claim:

l. The method of operating an electrode mounting for an electric furnacein which there is a fluid pressure cylinder for raising and lowering themounting, a source of fluid pressure connected with the cylinder to workin opposition to the weight of the electrode and its mounting with areversible pump controlled by power ow to the electrode operativelydisposed between the cylinder and fluid pressure source, which comprisescontinuously flowing the fluid from said source through said pump andcontinuously maintaining the pressure of the fluid from said source at apoint sufiicient to raise the electrode when the pump is not operating.

2. In an electric arc furnace, an electrode, a mounting for theelectrode, a servo-motor comprising a fluid-operated motor for raisingand lowering the mounting, a source of duid under pressure connectedwith the servo-motor, a reversible pump operatively connected lbetweensaid source and the servo-motor, said pump when idle transmittingpressure between the source and the servo-motor, and means formaintaining a lconstant pressure on said source sufficient to operatethe servo-motor to lift the electrode mounting when the pump is idle.

3. The method of operating an electric furnace electrode wherein theelectrode is carried on a support which is raised and lowered by afluidoperated motor, the fluid motor being connected with a source ofiiuid pressure with a reversible pump in the connection between thecylinder and the source of fluid pressure, the pump being drivenaccording to variations in currents applied to the electrode whichcomprises maintaining the source of fluid to operate the support under apressure sufficient to lift the electrode when the reversible pump isnot operating.

4. The method of operating an electric furnace electrode wherein theelectrode is carried on a support which is raised and lowered by a fluidpressure cylinder, the cylinder being connected with a source of fluidpressure with a reversible pump in the connection between the cylinderand the source of fluid pressure, the pump being driven according tovariations in currents applied to the electrode which comprisesmaintaining the source of fluid to operate the cylinder under a pressuresuicient to lift the electrode when the reversible pump is notoperating, while flowing the fluid through the pump as a metering meanswhereby such lifting of the electrode when the pump is not operatingoccurs slowly.

5. In the combination comprising an electric furnace electrode and itssupport, a fluid pressure cylinder for raising and lowering the support,a fluid reservoir, and a pipe connection between the reservoir and thecylinder including a reversible pump, the herein described inventionwhich comprises providing two pipe connections in the line leading fromthe pump to the reservoir, one of said :connections opening into thereservoir below the liquid level therein, and the other opening intothe'reservoir above the liquid level, there being an outwardly-openinginwardly-closing check valve in the first connection, and aninwardly-opening outwardly-closing check valve in the second connection,and a distributor in the reservoir to which the said second :connectiondelivers fluid.

6. In an electric fluid electrode operating mechanism wherein there isan electrode support, a fluid pressure cylinder for operating thesupport, a pipe for supplying liquid under pressure to the cylinder andwithdrawing liquid from the cylinder, a reversible motor to which saidpipe connects, and a fluid pressure reservoir, the reservoir having airunder pressure confined in the upper part thereof and a body of liquidin the lower part, the herein dened invention comprising a pipe leadingfrom the pump to the upper part of the reservoir and terminating in adistributor, there 'being a check valve in said pipe to prevent the flowof uid from the spray nozzle toward the pump, and a second pipe leadingfrom the pump to the lower part of the reservoir, there being a checkvalve in said second pipe through which nuid may flow from the reservoirto the pump, but which prevents the flow of fluid in the reversedirection whereby upon operation of the pump to supply liquid to thecylinder such liquid is withdrawn from the bottom of the reservoir andwhen the pump is operated to return the liquid to the reservoir it isforced through said nozzle whereby the heated oil being returned maythereby be cooled while the oil which flows from the reservoir is cool.

7. In an electrode operating system including an electrode support, aiiuid pressure cylinder for raising and lowering the support, a pipecommunicating with the cylinder, a reversible pump to which the pipeconnects, a iluid pressure reservoir connected to the other side of saidreversible pump, means for maintaining a body of air in the reservoirover the liquid for exerting a pressure upon the liquid greater thanthat required to elevate the electrode support, said reversible pumpbeing of the non-blocking type, hence when it is idle forming apassageway for a back-flow of fluid from the reservoir to the cylinderat a relatively small rate such as to slowly raise the electrodesupport.

WILLIAM E. MOORE.

